In all these experiments it is important to note when a commit of the
transaction is done. It is probably the case that autocommit is assumed
and each statement being discussed is a separate transaction. But
thought I would just raise the issue, derby definitely can not release
the space until the transaction doing the truncate commits. This is why
the extra files are created on truncate and drop, so that if necessary
we can abort the change by reverting back to the saved files.
The cleanup of these extra files happen at checkpoint time as that is
when we match up these objects with the transactions that created them
and if those transactions are committed or aborted then we can go ahead
and do the cleanup.
checkpoints happen automatically by the system at various times including:
o clean shutdown
o recurring while running based on amount of data logged
o when requested explicitly using procedure call
Maybe in your system with the system running "flat out" you are
automatically generating the checkpoints in the background and this is
the difference between what you and rick are seeing.
/mikem
Bergquist, Brett wrote:
My point Dag is that even though I did not checkpoint the database, Derby
released the disk space back to the OS (Solaris 10) when I dropped the table,
so my experience is not matching what Rick had mentioned in that the disk space
would not be released until a checkpoint. My experience is saying that the
disk space was released immediately.
Is there some implicit checkpoint being done? Note that my utility is
connecting to the database using the network server mode and the database was
not shutdown before the space was released back to the OS.
-----Original Message-----
From: Dag H. Wanvik [mailto:dag.wan...@oracle.com]
Sent: Tuesday, March 29, 2011 10:32 AM
To: derby-dev@db.apache.org
Subject: Re: Question about TRUNCATE TABLE and freeing disk space
"Bergquist, Brett" <bbergqu...@canoga.com> writes:
immediately brought this down to 46Gb of disk space. I do not have a
"checkpoint" in my utility application.
You can call it from ij or via JDBC:
"CALL SYSCS_UTIL.SYSCS_CHECKPOINT_DATABASE()"
http://db.apache.org/derby/docs/10.7/ref/rrefcheckpointdbproc.html
Dag
